The invention relates to an arrangement for open-end friction spinning devices of the type having two adjacently arranged friction rollers driven in the same rotational direction and forming a wedge-shaped gap serving as the yarn formation region. A fiber feed channel extends along a fiber dispersion zone into the area of the wedge-shaped gap and serves as the transport means for the fiber material which has previously been opened up into single fibers. A suction device is provided for producing a suction air stream directed into the wedge-shaped gap and serving to retain the fibers and the yarn being produced in the wedge-shaped gap. Also an air supply device is provided for producing a compressed air stream directed against the area of the wedge-shaped gap. Finally a yarn withdrawal device is provided for withdrawing the produced yarn in the longitudinal direction of the wedge-shaped gap.
With a known arrangement of the above-mentioned kind described in German Published Unexamined Application (DE-OS) No. 33 08 250 and the corresponding U.S. Pat. No. 4,483,136, an air inlet opening is arranged on the side adjacent the mouth of the fiber feed channel in the area of the friction roller which rotates out of the wedge-shaped gap, which air inlet opening produces an air inlet flow which is enhanced under certain conditions by the compressed air. This air inlet stream facilitates loosening of any fibers that were carried along by the cover surface of the roller rotating out of the wedge-shaped gap, and to return said fibers into the yarn formation region so that the same can be twisted into the forming yarn. The slot-shaped air inlet opening may extend with this kind of construction even beyond the so-called fiber dispersion zone along the mouth of the fiber feed channel, whereby the produced yarn is retained within the wedge-shaped gap. With this construction it is provided that the additional air stream is first directed towards the cover surface of the roller rotating out of the wedge-shaped gap, and then deflected.
It is an object of the present invention to provide for an arrangement of the above-mentioned kind in such a manner that the spinning conditions can be influenced by providing an additional air stream.
This object is achieved in accordance with the invention by providing that the air inlet device includes at least one compressed air jet or nozzle extending into the plane of the wedge-shaped gap and being directed upon the yarn, thereby influencing the contact force of the yarn against the rollers.
This arrangement first makes it possible to influence the contact of the yarn against the rollers and thereby also to influence the friction effect upon the produced yarn.
In a further development of the invention, it is provided that the mouth or opening of the compressed air jet is arranged in direct proximity to the yarn being produced within the wedge-shaped gap. This will allow positive adjustment of the effect of the compressed air jet or the compressed air jets without disturbing the surrounding areas.
In a further development of preferred embodiments of the invention, it is provided that at least one compressed air jet follows the dispersion zone in the yarn withdrawal direction and is arranged on the same side of the wedge-shaped gap as the fiber feed channel. It is thereby possible to increase the friction effect in the area essential for the twisting process, in which area the full fiber amount is supplied to the yarn. It is thereby attained that the twisting is introduced more securely into the yarn and unsteady motions of the yarn in its axial direction are avoided. In a further advantageous development of preferred embodiments of the invention, it is provided that a draw-off suction device is arranged on the side of the wedge-shaped gap opposite the compressed air jet for facilitating the withdrawal of the supplied air.
In a further development of preferred embodiments of the invention, it is provided that at least one compressed air nozzle or jet is arranged at the side of the wedge-shaped gap facing away from the fiber feed channel, which jet is directed toward the beginning portion of the produced yarn. It is thereby possible to influence the position of the yarn tip in which the yarn does not contain the full amount of fibers such that the yarn tip is not too far drawn into the wedge-shaped gap. Any relative movements of the yarn tip compared to the rest of the yarn and the occurrence of thinning portions or even yarn breaks are thereby avoided. The yarn tip is positioned essentially in line with the extension of the produced yarn within the wedge-shaped gap. It is then advantageous if the blowing direction of the compressed air jet arranged at the side of the wedge-shaped gap facing away from the fiber feed channel is inclined against the yarn withdrawal direction. One thereby influences the tensile stress in the produced yarn and furthermore the yarn strength.
In another development of the invention, it is provided that the compressed air jets are equipped with adjusting elements for adjusting same with different blow pressures and/or blow quantities. This enables one to measure the effects and especially to make any adjustment as different fiber material is spun at a given time. It is likewise advantageous for the same purpose if, according to a further development of preferred embodiments of the invention, the compressed air jets are disposed in such a manner that their distance to the yarn and/or their inclination to the yarn withdrawal direction and/or their distance to the mouth of the fiber feed channel are adjustable.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, an embodiment constructed in accordance with the present invention.